I have an 04 4.7L V8 Limited with 205K.

My A/C generally cools OK, but the compressor cycles on and off frequently (5-10 seconds). Over the past couple of years, I've had to add refrigerant a couple of times to get it to cool well. I now have access to an A/C machine so I decided to recover the refrigerant and start from zero to get the right charge.

I recovered 1.50 lbs and 3 oz of oil from the car and evacuated it for 30 mins. I left vacuum on it overnight and it held, so I decided to recharge.

Per the placard, the min charge is 1.21 lbs and the max is 1.43. I put in 3 oz of PAG 46 and charged it to 1.43 lbs.

Temps are around 60F today. Static pressure is around 60 psi. When I turned on the A/C, the compressor kicked on and the high side climbed up to around 105 psi while the low side dropped to almost 10 psi before the compressor kicked out. The cycle continues indefinitely. I tried replacing the relay with no change. Thinking the pressures were too low, I added another 0.2 lbs of freon. The pressures increased, but the cycling continued.

Looking for any ideas on what to check. Right now, I recovered and evacuated the freon again.

Use the sight glass on the high side. I had the same issuse and just needed to add a few more ounces. But the sight glass makes it easy.

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Cycling is a part of how A/C systems work...otherwise they would just build pressure indefinitely. But I gather from your post you know a little about A/C systems. 5-10 seconds sounds like short cycling. It could be from a low charge (perhaps the scale in the AC machine you used is not working properly)... I would keep adding 2 tenths of a pound until you get the low side to about 25psi and the high side at 135 on a 60* day. If it still isn't cool at those pressures, or it is still short cycling you have another issue. Here are the charts I use when diagnosing A/C systems.

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Thanks for the information. I ended up recharging it to the max charge level and just running it for a few days. So far it seems to be cooling ok. Maybe the cycling was a function of the temperature. After checking the charts, the pressures seem to line up. Thanks for that!